In existing networks, the spectral grids corresponding to the spectral distribution of these channels are grids comprising a fixed space of 50 or 100 GHz between channels as defined by the standards of the International Telecommunications Union. Such a standard spacing makes it possible to facilitate the detection of end signals, but leads to a waste of the available bandwidth. This is because the signals intended to be transmitted on these channels do not all have the same characteristics, such that the optical paths that they must take may have different characteristics. Thus, one means of optimizing the use of available spectral band is to propose a grid whose spacing between the channels is no longer uniform and fixed, but rather variable and adaptable to the characteristics of the signals and/or connections, thereby making it possible to reduce whenever necessary the spectral spacing in order to transmit a greater quantity of signals over the same spectral band. Nonetheless, the use of such a variable grid comprising reduced spectral spacings leads to increase in the crosstalk between adjacent channels during the transmission of the signals, leading to a reduction in the quality of the end signals.
The need is therefore to propose a method for reducing crosstalk between adjacent channels when a variable spectral grid is used whose spectral spacings may be reduced compared to standard spectral spacings.